Late Holocene glacial history of Manatee Valley, Upper Lillooet Provincial Park, southern Coast Mountains, British Columbia

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Upper Lillooet Provincial Park,

Southern Coast Mountains, British Columbia

By

Lindsey Koehler

B.Sc., University of Puget Sound, 2004

A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of

Masters of Science

in the Department of Geography

 Lindsey Koehler, 2009 University of Victoria

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Supervisory Committee

Late Holocene Dendroglaciologic History of Manatee Valley, Upper Lillooet Provincial Park,

Southern Coast Mountains, British Columbia

by

Lindsey Koehler

B.Sc., University of Puget Sound, 2004

Supervisory Committee

Dr. Dan Smith (Department of Geography)

Supervisor

Dr. Jim Gardner (Department of Geography)

Departmental Member

Dr. Richard Hebda (School of Environmental Studies)

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Abstract

Supervisory Committee

Dr. Dan Smith (Department of Geography)

Supervisor

Dr. Jim Gardner (Department of Geography)

Dr. Richard Hebda (School of Environmental Studies)

This investigation uses dendrochronologic and radiometric techniques to infer the timing of glacier advance for four ice lobes that are drained by Manatee Creek in a remote valley located in the southern Coast Mountains, British Columbia.

Dendroglaciologic evidence exposed by retreating glaciers provides evidence for

increasing complexity in the Holocene glacial record, particularly for mid-late Holocene events. Since Holocene ice fronts periodically extended below treeline in the region, previous glacier advances overrode and buried forests beneath till deposits. The dendroglaciologic evidence presented here corroborates the record of glacier advances described for other southern British Columbia Coast Mountain glaciers and details ice front position at ca. 4270 14_{C yr BP, 3430}14_{C BP and 2350}14_{C yr BP. Well-preserved} sequences of lateral, nested moraines were mapped and profiled to delineate the

boundaries of Manatee and Oluk glaciers. Relative dates provided by lichenometry and dendrochronology were used as limiting dates for the deposition of 5-6 moraines during the late 14th_{, early 16}th_{, early 18}th_{, 19}th_{, and early-20}th_{Century. Reconstructions of} Holocene glacial history offer insight into the regional, climatic regime and add to the discussion about pervasive, millennial-scale cycles.

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List of Figures

Figure 3.1. Map of the Manatee valley study area, located in the southern Coast

Mountains of B.C. The forefields and lateral moraines of four of the glaciers that drain via Manatee Creek were investigated for this study: Orca (unofficial), Beluga

(unofficial), Manatee, and Oluk glaciers. Features and sampling locations have been superimposed on the 1970 Canada topographic series 92J/12 map...39 Figure 3.2. Orca Glacier released several pieces of detrital wood into the headwaters of

Manatee Creek in (Site 1). The outermost rings of two subfossil trees were radiocarbon dated at 3500±60 14_{C yr BP (MC06-27) and 4270±60}14_{C yr BP (MC06-03). The} foreground shows the western lateral moraines formed by the confluent ice front of Orca and Beluga glaciers during the late-LIA (Site 5)...48 Figure 3.3. A buried subalpine tree located along the proximal slope of the eastern lateral

moraine of Manatee Glacier. This sample (MC06-07) was killed in 3430±60 14C yr BP, when ice almost thickened to late-LIA proportions...50 Figure 3.4a. Subfossil subalpine fir stump (MC06-23) found rooted in a paleosol within

the Orca/Beluga glacier forefield (Site 3). A sample of perimeter wood had a

radiocarbon age of 2350 ±70 14_{C years BP...52} Figure 3.4b. A glacially-sheared subalpine fir tree (MC07-22) found in a near-growth

position below Manatee Glacier (Site 4). The sample cross-dated with the radiocarbon controlled floating subalpine fir chronology constructed from samples collected at Site 3...53 Figure 3.5a. The construction of the late-LIA moraine buried this subalpine fir tree

(MC06-04) along the western marginal of Orca/Beluga glacier in 1738 AD (Site 5)...54 Figure 3.5b. Standing snag (MC06-06) located adjacent to the distal slope of the western

lateral moraine of Orca/Beluga glacier (Site 5). The tree died in 1736 AD following the deposition of the moraine...55 Figure 3.6. Rhizocarpon geographicum growth curve for the Mt. Waddington area

revised with control points from this study and additional data from Larocque and Smith (2004)...58 Figure 3.7. Topographic cross-sections of the lateral moraines surveyed on the northern

and southern margins of Manatee Glacier and the southern boundary of Oluk Glacier (see Figure 3.1 for transect locations). The moraines are numbered so that M1 is always in the most distal. Numbers from different transects are not necessarily time synchronous...61

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Figure 3.8. This figure compares the growth trends of the living Abies lasiocarpa

chronology collected in Manatee Valley to lateral moraine dates that were determined with lichenometry along the margins of Manatee and Oluk glacier (see Figure 3.1 for exact location). The thick black line represents a 10-year moving average. Plotted on the right-hand axis is the number of series in the master chronology. Each grey rectangle spans 25-year intervals that are centered on a lichenometric dates for each moraine...68 Figure 4.1. Relief map of British Columbia including the location of previous studies that

investigate environmental changes in the alpine during the Holocene: Eastern Pacific Ranges(Lillooet, Bridge, Manatee glaciers); Central Coast Mountains (Tiedemann glacier, Mt. Waddington area); Garibaldi Provincial Park (Garibaldi, Fitzsimmons, and Spearhead ranges); Insular Ranges (Strathcona Provincial Park); Heal Lake; Boundary Ranges (Todd Valley, Tide Lake, Jacobsen glacier)...80 Figure A.1 (continued) Subalpine fir master tree-ring chronology (residual and ARSTAN version...103 Figure A.1. Subalpine fir master tree-ring chronology (raw and standardized versions).

102

Figure B.1. Subalpine fir floating chronology (raw and standardized versions)...105 Figure B.1. Subalpine fir floating chronology (residual and ARSTAN versions)...106

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List of Tables

Table 3.1. Rates of linear recession of Manatee Valley glaciers over the 20th Century, as calculated from historical photographs...40 Table 3.2. Control sites used to determine tree and lichen ecesis intervals within the

Manatee Glacier forefield...46 Table 3.3. Chronology statistics for the two subalpine fir collections from Manatee

Valley. The first collection is the master dating series, while the second is a floating chronology of subfossilized wood recovered at Sites 3 and 4...47 Table 3.4. Summary of radiocarbon dated, dendroglaciologic evidence recovered in

Manatee Valley...56 Table 3.5. Lichenometric dates derived for lateral moraine stabilization at Manatee

Glacier and Oluk Glacier. Transect locations and orientations are displayed in Figure 3.1. Minimum dates for moraine stabilization incorporate systematic errors associated with the Rhizocarpon geographicum growth curve from the central Coast Mountains (Larocque and Smith, 2004\; Smith and Desloges, 2000)...62 Table 4.1. Summary table of Holocene glacier advances in the B.C. Coast Mountains...81

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Acknowledgments

I would like to express my gratitude to a number of people who helped me complete this thesis. Dan, thank you so much for the opportunity to explore the

mountains of B.C. and for bringing together such an amazing group of girls. I truly could not have asked for a more fun and supportive supervisor. Thanks to everyone who helped me in the field. Kelly and Michi, thanks for teaching me not to (always) follow Dan. Bethany and Leslie, your perseverance through 8 days of rain and crumbling moraines in 2007 was more than I ever could have expected. Thanks to Aquila, Lisa, Trisha, Sarah, and Kate for endless laughter in the lab and having, the occasional, valuable discussion about dendrochronology. I will miss you all very much!

There are, of course, several other individuals who offered their continued support. Mom and Dad, thanks for your encouragement and financial support. Mike and Lisa, you have undeniably played important roles throughout this experience. Thank you for believing in me and making home, home.

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Chapter 1: Introduction

Documentation of glacier extent and volume changes over the last half century in Pacific North America demonstrates that most have experienced significant frontal retreat and downwasting (Scheifer et al., 2007; VanLooy and Forster, 2008). Some of the most rapid changes in western Canada have occurred in the southern cordillera where a 12.5% decrease in ice-cover has occurred since 1985 (Bolch et al., 2008). Researchers have often used instrumental mass balance records from southern British Columbia (B.C.) to describe the attendant glacier mass balance linkages with climate on interannual

(Letréguilly, 1988; Bitz and Battisti, 1999), decadal, and multi-decadal time-scales (Hodge et al., 1998; Kovanen, 2003). Assessing the response of glaciers to climate prior to the mid-20th_{Century, however, necessitates reconstruction of centennial to millennial} length proxy records (Bradley and Jones, 1993).

Research Background

Decreasing glacier cover since the beginning of the 20th_{Century has been}

described as hemispheric in scale, probably relating to increased global air temperatures (Oerlemans, 2005). Given the regional nature of the glacier-climate relationship, it is reasonable to assume that the distribution of moraines within glaciated valleys provides a long-term perspective of alpine environmental conditions during the late-Holocene. The prevalence of intact moraine sequences in Pacific North America overcomes the poor spatial and temporal coverage of documented records to provide relatively detailed glacier histories by applying tephrochronologic, dendrochronologic, and lichenometric

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dating techniques (Grove, 1988).

Retreating glaciers in the Coast Mountains regularly expose the remains of forests buried by past advances (Mathews, 1951). These subfossil remains have successfully been interpreted using dendroglaciology to detail ice front fluctuations spanning the Holocene interval (Ryder and Thomson, 1986; Luckman, 2000; Menounos et al., in press). The purpose of this thesis is to describe the prehistoric behaviour of glaciers located in a remote headwater area of the southern Coast Mountains and gain insight into low frequency climate variability in the North Pacific. The intent was to use

complimentary dendroglaciological and lichenometric methodologies to present a chronology of late-Holocene glacier activity.

Research Objectives

Given the research needs of the region, the primary objectives of this research were to:

1. Reconstruct glacial fluctuations at Manatee Valley in the Coast Mountains of southern B.C. over the Holocene by: a) applying dendroglaciologic and radiometric techniques to determine the extent and timing of former glacier advances; and b) employing lichenometric techniques to date the stabilization of lateral moraine complexes.

2. Compare the findings of these investigations with existing glaciological and paleoenvironmental records from other locations in B.C., Alberta, Alaska, and Washington State (WA) in order to identify common intervals of glacier advance and any elucidate spatial relationships.

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Thesis Overview

This thesis is organized into five chapters. Following this introduction, Chapter Two provides historical context for glaciologic research in western Canada and reviews current dendroglaciological investigations, particularly those undertaken in the Coast Mountains. A brief review of dendroglaciology and lichenometry are also included in this chapter to provide a background for interpreting reconstructions of glacier activity. Chapter Three describes the main findings of this research, and was prepared as a manuscript for submission to a peer-reviewed professional journal. Chapter Four provides an expanded discussion of the results and compares the findings with those of previous studies in the Canadian Cordillera, WA, and Alaska. Chapter Five, summarizes the main conclusions of the research, discusses some of the limitations, and offers suggestions for future dendroglaciological research in B.C. Supplementary data is included in the Appendices.

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Works Cited

Bitz, C.M., and Battisti, D.S., 1999. Interannual to decadal variability in climate and the glacier mass balance in Washington, western Canada, and Alaska. Journal of Climate, 12: 3187-3196.

Bradly, R.S., and Jones, P.D. 1993. 'Little Ice Age' summer temperature variations: their nature and relevance to recent global warming trends. The Holocene, 3: 367-376.

Bolch, T., Menounos, B., and Wheate, R. 2008. Remotely-sensed Western Canadian Glacier Inventory 1985-2005 and regional glacier recession rates. Geophysical Research Abstracts, 10: EGU2008-A-10403.

Grove, J.M. 1988. The Little Ice Age. Methuen, London, UK.

Hodge, S.M., Trabant, D.C., Krimmel, R.M., Heinrichs, T.A., March, R.S., and Joseberger, E.G. 1998. Climate variations and changes in mass of three glaciers in western North America. Journal of Climate, 11: 2161-2178.

Kovanen, D.J. 2003. Decadal variability in climate and glacier fluctuations on Mt Baker, Washington, USA. Geografiska Annaler, 85A: 43-55.

Letréguilly, A. 1988. Relation between the mass balance of western Canadian mountain glaciers and meteorological data. Journal of Glaciology, 34: 11-18.

Luckman, B.H., 2000. Little Ice Age in the Canadian Rockies. Geomorphology, 32: 357-384.

Mathews, W.H. 1951. Historic and prehistoric fluctuations of alpine glaciers in the Mount Garibaldi map-area, southwestern British Columbia. Journal of Geology, 59: 357-380. Menounos, B., Osborn, G., Clague, J., and Luckman, B. In press. Latest Pleistocene and Holocene glacier fluctuations in western Canada, Quaternary Science Reviews, 30. Oerlemans, J. 2005. Extracting a climate signal from 169 glacier records. Science, 308: 675-677.

Ryder, J.M., and Thomson, B. 1986. Neoglaciation in the southern Coast Mountains of British Columbia: Chronology prior to the late Neoglacial maximum. Canadian Journal of Earth Sciences, 23: 273-287.

Schiefer, E., Menounos, B., and Wheate, R. 2007. Recent volume loss of British Columbian glaciers, Canada. Geophysical Research Letters, 34: L16503.

VanLooy, J., and Forster, R. 2008. Glacial changes of five southwest British Columbia icefields, Canada, mid-1980s to 1999. Journal of Glaciology, 54: 469-478.

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Chapter 2: Review of Dendroglaciologic and Lichenometric

Research in Pacific North America

Introduction

Since the retreat of the Late Wisconsin Cordilleran Ice-Sheet in Pacific North America (PNA) from its maximum extent after 15,000 cal. yr BP (Blaise et al., 1990), alpine basins in this region have experienced several glacial advance intervals, most notably during the late-Holocene Little Ice Age (LIA) interval. Grove (1988) reviews the LIA as a concept global in scale, although the supporting data are heavily biased towards European glaciers. Documentation of down valley ice extent for North American glaciers is typically limited to the 20th_{Century. Fortunately, the ongoing discovery of datable} organics within the forefields of glaciers in PNA is offering the opportunity to construct relatively detailed Holocene glacial histories. Geobotanical methods, such as

dendrochronology and lichenometry, have commonly been used to characterize the Holocene behaviour of alpine glaciers in the region (Grove, 1988). The key concepts and assumptions of these methodologies are reviewed in this chapter. The chapter also provides an historical framework for Holocene glacial research in the Canadian Cordillera and a review of the current state of knowledge.

Review of Methods Dendroglaciology

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reconstruct past glacier activity (Smith and Lewis, 2007). This approach to event dating rests foremost on the assumption that trees in the higher latitudes form early-wood and late-wood cells in tree-rings annually; and, second that tree ring-widths vary in response to limiting factors (ie. temperature and/or precipitation climate) to create distinctive time series (Fritts, 1976). Complete reviews of dendroglaciology methodologies and

applications are available in Schweingruber (1988) and Luckman (1988). This review considers only those concepts necessary to guide the interpretation of the glacier history reconstructions that follow.

Dendroglaciology allows for the dating of glacier activity by:

1. Determining minimum ages for glacial landforms with annual ring counts of the oldest tree inhabiting deglaciated terrain, referred to herein as the geobotanical approach (Lawrence, 1946; Heusser, 1956).

2. Establishing the calendar year of glacial advance into ice-marginal forests, through the selection of trees exhibiting callous tissue, corrasion scars, or reaction wood, which demonstrate abnormal cell development in response to encroaching glaciers (Alesto, 1971; Schroder, 1980; Luckman, 1988; Wiles et al., 1996).

3. Resolving the year of death of glacially overridden trees by cross-dating, a process that involves comparing ring-width patterns, between living and glacially reworked trees (Schweingruber, 1988; Luckman, 1995).

4. Applying radiometric dating to the perimeter wood of subfossilized samples, when ring-widths fail to cross-date with a master chronology, or when the preservation of wood is poor (Wood and Smith, 2004).

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episodes (LaMarche and Fritts, 1971; Scuderi, 1987; Wiles et al., 1996); b)

instrumental mass balance records (Lewis and Smith, 2004a; Watson and Luckman, 2004); and/or, c) climate records (Villalba, et al., 1990; Larocque and Smith, 2005).

Although dendroglaciology benefits from simplicity and low cost, several limitations are worth noting. The success of dendroglaciological research depends upon an abundant supply of wood and the subsequent preservation within actively eroding proglacial environments (Luckman, 1988). Dendroglaciologic interpretations are also restricted in their temporal range. For example, the success of cross-dating depends upon the longevity of local trees, which often fail to exceed 300-400 years in many subalpine locations (Schweingruber, 1988). Nonetheless, millennial length chronologies have been compiled for a few glaciated valleys in PNA (Scuderi, 1987; Barclay et al., 1999, 2009). Limitations to dendroglaciological dating arise because: a) intercepting the pith when coring a tree is rare, especially for large diameter trees (Villalba and Veblen, 1997); b) extracting cores from the root ball is challenging (McCarthy et al., 1991; Wincester and Harrison, 2000); c) tree-ring series sometimes contain missing and/or false ring boundaries, resulting in incorrect age determinations; and most importantly, d) opportunities for determining locally relevant ecesis intervals, the time it takes for seedlings to establish, are often limited by the lack of reliable control surfaces and/or inconsistent colonization rates due to microclimatic effects (Sigafoos and Hendricks, 1969; Villalba et al., 1990; McCarthy and Luckman, 1993; Koch, 2009).

Over the past century, glaciologic studies from the Canadian Cordillera have contributed greatly to research efforts concerned with providing detailed reconstructions of late-Holocene glacier activity (Clague and Slaymaker, 2000). Glaciers in this region

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have regularly interacted with subalpine forests, and late-Holocene glacial sediments are well-preserved. Lawrence (1946) was the first to apply tree-ring dating techniques to date glacial landforms in the Olympic Mountains, Washington State (WA). Following his application, dendrochronological research methodologies were applied in the Garibaldi Range, B.C. (Mathews, 1951; Brink, 1959), and in the Canadian Rocky Mountains (Heusser, 1956; Bray and Struik, 1963; Luckman and Osborn, 1979). In both regions, extensive LIA advances obliterated most pre-existing moraine sequences, therefore precluding insight into the magnitude of pre-LIA events.

Dendroglaciology provides a number of opportunities for dating glacier events (Luckman, 2000; Smith and Lewis, 2007). Overridden forests provide information about the timing of onset, culmination, and duration of glacial events. Subfossilized wood samples recovered from a glacier forefield that lack a direct association with glacial sediments, are helpful in providing limiting dates for advancing ice snouts. Glacially-sheared in-situ stumps provide direct evidence of an advance and demarcate the position of a former glacier margin (Luckman, 1995; Wood and Smith, 2004). The timing of maximum ice cover, or culmination, can be estimated by dating trees that are found growing on recently deglaciated surfaces or on stabilized moraine complexes (Luckman, 1988). In addition, many lateral moraine sites in the Canadian Cordillera display stacked tills and woody detritus interbedded with paleosols. When combined with radiometric dating, the stratigraphic records exposed in these moraines, have been interpreted to extend the temporal range of dendroglaciology to span millennia (Osborn et al., 2001; Reyes and Clague, 2004; Jackson et al., 2008).

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Lichenometry

Lichenometry is a relative dating methodology that is employed to estimate minimum dates for the surface stabilization of moraines (Andrews and Weber, 1969; Innes, 1985). Beschel (1950, 1961) pioneered lichenometric dating, and was the first to investigate the relationship between thallus age and diameter on moraine surfaces.

Although lichenometry applies best to moraine sequences dating to the last 500 cal. years (Innes, 1985), surfaces up to 900 years old have been dated by extrapolating growth-rates with radiometrically-dated control surfaces (Larocque and Smith, 2004). Detailed

reviews of lichenometry are available from several authors (Jochimsen, 1973; Innes, 1985; 1988). The key assumptions are:

1. Thallus expands radially at a constant rate.

2. Thallus size, measured in terms of maximum diameter, is directly related to the surface age of a deposit (Beschel, 1961).

3. The age of the reference surface is known to the calendar year.

4. Individual thalli can be identified at least to the subspecies level (Benedict, 1988). 5. The methods for data collection and the character of sampling sites, selected for lichenometric work are comparable between reference surfaces and surfaces with unknown age.

The first assumption is often the most difficult to substantiate because of uncertainties about the life history of lichen species in relation to climatic effects. Although Porter (1981) and others have quantified the relationship between lichen growth and macro-scale climate, microclimatic effects can also contribute to anomalous

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growth (Jochimsen, 1973). The microclimatic factors shown to influence thallus growth rates include: moisture availability, the substrate aspect, duration of snow-cover, and fertilization from alpine inhabitants (Porter, 1981; Smith et al., 1995; Lewis and Smith, 2004b). Microclimate, however, has a less pronounced effect on the age assigned by lichenometry to a substrate when the search area is increased (Innes, 1988).

A key assumption of lichenometry is that thalli display a predictable rate of growth with time. The most commonly adopted growth-rate curve is that of a second-order polynomial that presumes slow rates of thallus expansion during a phase of initial establishment, later acceleration during the “great period”, and finally decreasing rates of growth during the “senescent” phase (Beschel, 1961; Andrews and Webber, 1969; Porter, 1981; Innes, 1988). Although the range of age-growth relationships adopted for

lichenometric work suggest this may not always be the case (Armstrong, 2005), only limited research has focused on establishing lichen growth rates by direct observation (McCarthy, 2003; Armstrong, 2005; Bradwell and Armstrong, 2007).

Another major limitation of lichenometric studies has been a lack of consistency among the sampling methods used to establish age-size relationships (Innes, 1985). Two distinct sampling protocols have been reviewed by Innes (1988) and Karlén and Black (2002). The traditional method proposed by Beschel (1950, 1961) requires the

development of a relationship between thallus expansion on surfaces of unknown age and substrates of known age. This indirect method, although benefiting from simplicity, does not allow for the assignment of confidence intervals based upon normal population structures. The size-frequency and percent-cover approach, on the other hand, does allow for statistically defined estimates of uncertainty (Locke et al., 1979; McCarroll, 1994).

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Unfortunately this technique is time-consuming and requires a substantial number of samples.

Lichenometric growth curves have been developed for Rhizocarpon

geographicum (L.) DC for several locations in the mountains of western North America. In the Coast Mountains, the growth curve established by Smith and Desloges (2000) near Bella Coola was modified with additional data provided by Larocque and Smith (2004) from the nearby Mt. Waddington Range. Independent growth curves have been

developed for the Insular Ranges on Vancouver Island (Lewis and Smith, 2004b) and for the Cascade Range, WA (O'Neal and Schoenenberger, 2003). The latter growth curve is notable for the rapid rate of expansion shown by lichens growing on Mounts Baker, Hood, and Rainier. All of these curves have been assessed for their ability to date

moraine sequences in the southern Coast Mountains (Allen and Smith, 2007; Koch et al., 2007a).

Holocene Glacial Activity in the B.C. Coast Mountains

Following the disintegration of the Cordilleran Ice-Sheet, valley glaciers in coastal B.C. rapidly decayed to present day extents by ca. 9500 14_{C yrs BP (Fulton, 1971;} Clague, 1981; Friele and Clague, 2002), which broadly corresponds with the arbitrary definition set forth by Hopkins (1975) for the beginning of the Holocene Epoch.

Intact lacustrine sediments contain paleobotanical evidence that characterizes the early-Holocene as having relatively warm and dry conditions compared to those present today. Defined as the “Hypsithermal” by Deevey and Flint (1957) for eastern North America, this term has restricted utility in the coastal ranges of B.C. because of its

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time-trangressive character (Mathewes, 1985). Hebda (1995) sought to resolve some of these conflicting interpretations from B.C. paleoecological records by subdividing the early-Holocene into a warmer and drier “xerothermic” and a warm, moist “mesothermic” interval. Following this interval, glaciers in the region began advancing, presumably in response to the deteriorating climatic conditions, marking the onset of the “Neoglacial” in the southern Canadian Cordillera by 5000 14_{C yrs BP (Porter and Denton, 1967;} Denton and Karlén, 1973a). Compositional changes in vegetation assemblages

surrounding high elevation lakes in B.C. mountains, however do not show adjustments until 4400-3700 14_{C yrs BP (Hebda, 1995; Spooner, 2002; Heinrichs et al., 2004). In this} review dates are represented in 14_{C yrs BP for most episodes of Holocene glaciation.} Wood ages assigned to the LIA, and those that have been securely cross-dated with master chronologies, are herein reported in calendar years AD.

Early-Holocene Advances

Preservation of early-Holocene deposits is rare in glaciated basins, requiring researchers to obtain paleoenvironmental records from down valley sedimentary sinks. With the prevalence of warm and dry climatic conditions evident from lacustrine and marine records (Mathewes, 1985; Pellatt et al., 2000; Palmer et al., 2002; Spooner et al., 2002), the expansion of alpine glaciers was, presumably, not climatically facilitated in the early-Holocene (Davis and Osborn, 1987; Clague and Mathewes, 1989). Nonetheless, detrital wood found within glacier forefields in the southern Coast Mountains has been interpreted in concert with lacustrine records to suggest a short-lived glacial advance at 7770- 7380 14_{C yrs BP, coeval with the 8200-year cold event defined from Greenland ice}

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cores (Reasoner et al., 2001; Menounos et al., 2004). Thomas et al. (2000) offer evidence for tephra-constrained till units that demonstrate a considerable depression in glacial limits at this time on Mt. Baker. This finding agrees with the ages assigned to charcoal-bearing moraines located on Glacier Peak (Begét, 1981) and Mt. Rainier (Heine, 1998) in the Cascade Mountains. This event is also possibly synchronous with till units deposited before the deposition of Mazama ash at sites located in the Canadian Rocky Mountains (Luckman and Osborn, 1979).

“Garibaldi Phase”

In-situ glacially deposited wood recovered from sites in Garibaldi Provincial Park dating to 6000-5300 14_{C yrs BP provides the first indication of a mid-Holocene glacier} advance (Stuiver et al., 1960; Lowdon and Blake, 1968, 1975). Ryder and Thomson (1986) identified this interval as the “Garibaldi Phase”, and not an “advance”, as the sites lacked an association with corresponding down valley till deposits.

“4200 yrs. BP Event”

Dendroglaciologic evidence from the southern B.C. and Alberta has been reinterpreted along with recent radiocarbon evidence and paleolimnological records to identify at least two glacier advances between 4200-3500 14_{C yrs BP (Menounos et al., in} press). The onset of this glacial interval is indicated from interpretations of the origin of detrital wood recovered from the forefields of Sphinx, Helm, (Koch et al., 2007a), Spearhead (Osborn et al., 2007), and Goddard glaciers (Menounos et al., 2008). The earliest phase of this advance at ca. 4200 14_{C yrs BP is indicated within lake sediment}

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records. It is suggested that this period of ice expansion was restricted and did not see glaciers advance to positions near those attained in the late-Holocene. Correlative support for the regional significance of this event comes from evidence recovered at glaciers located in the Interior Ranges of B.C. and the Canadian Rocky Mountains (Menounos et al., in press). During a readvance at ca. 3800 14_{C yrs BP, several glacier termini reached} down valley positions close to those reached in the LIA in southern B.C.(Menounos et al., 2008; in press). High elevation lake sedimentation rates during this interval

correspond in rate and magnitude to those associated with LIA glacial activity (Menounos et al., 2008).

“Tiedemann Advance”

The most widely recognized late-Holocene period of pre-LIA glacier expansion is the Tiedemann Advance. This episode of glacier advance was originally proposed to have occurred between 3300 to 1900 14_{C yrs BP (Ryder and Thomson, 1986). Recent}

investigations have since confirmed the regional nature of this event in the B.C. Coast Mountains (Clague and Mathews, 1992; Clague and Mathewes, 1996; Reyes and Clague, 2004; Laxton, 2005; Allen and Smith, 2007; Koch et al., 2007b; Osborn et al., 2007; Jackson et al., 2008). The “Tiedemann Advance” is considered to be coeval with the “Peyto Advance” of the Canadian Rocky Mountains (Luckman and Osborn, 1979; Osborn and Karlstrom, 1989; Wood and Smith, 2004).

“Unattributed Advance”

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1900 14_{C yrs BP time. In-situ ice-associated wood radiometrically dated to 1900}14_{C yrs} BP has been obtained from the lateral flanks of Todd Valley in the northern Coast Mountains (Laxton, 2005; Jackson et al., 2008). Detrital wood from the southern Coast Mountains dating to this period has been retrieved from sites in the Bridge River valley (Allen and Smith, 2007) and from within the Lillooet Glacier lateral moraine (Reyes and Clague, 2004). Although no evidence has been discovered regarding the extent of ice around 2300 14_{C yrs BP, the close association with underlying paleosols at all of these} sites indicates that environmental conditions ameliorated long enough to allow for tree establishment on Tiedemann-age deposits.

First Millennium Advances (FMA)

Reyes et al. (2006) provide an extensive review of the available evidence for multiple episodes of ice extension during the First Millennium AD in PNA. Radiocarbon dated organics from numerous glacier forefields suggest ice began advancing from 1900-1750 14_{C yrs BP (200 to 300 AD), and reached its maximum extent ca. 1600-1250} 14_{C yrs BP (400 to 700 AD) (Reyes et al., 2006). In the eastern Pacific Ranges, this event} was identified as the “Bridge Advance” based on glacially-sheared in-situ stumps

collected by Allen and Smith (2003) at the type location below Bridge Glacier. Since this initial discovery correlative glacier advances have been described from the Lillooet Glacier forefield (Reyes and Clague, 2004), at sites located in Garibaldi Provincial Park (Koch et al., 2007b), at sites located in the Northern Boundary Ranges (Laxton, 2005; Jackson and Smith, 2008), and in Alaska (Calkin et al., 2001; Wiles et al., 2008). The remains of a forest overrun by the Tebenkof Glacier, in Alaska's Kenai Mountains, were

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cross-dated into a millennial length chronology to show that the glacier was advancing down valley between 710's to 720's AD (Barclay et al., 2009). Although direct evidence for moraine construction during the First Millennium is generally lacking, Denton and Karlén (1973b) have presented lichenometric dates on moraines from the St. Elias Mountains that correlate with the FMA.

Little Ice Age

Most fresh-looking till and moraine deposits found within the Canadian Cordillera are attributed to LIA glacier advances (Luckman, 2000). Although the most extensive LIA moraines in the southern Coast Mountains were constructed by the early 18th_{Century in the southern Coast Mountains, moraines from earlier LIA advances have} been preserved in some locations.

Research into LIA glacier behaviour has been completed in the southern Coast Mountains (Pacific Ranges: Ryder and Thomson (1986); Mt. Waddington Range: Larocque and Smith (2003); Vancouver Island Insular Mountains: Lewis and Smith (2004a, 2004b); Eastern Pacific Range: Reyes and Clague (2004) and Allen and Smith (2007); Garibaldi Range: Koch et al. (2007a); and in the northern Coast Mountains (Desloges and Ryder, 1990; Clague and Mathews, 1992; Clague and Mathewes, 1996; Laxton, 2005; Lewis and Smith, 2005; Jackson et al., 2008). Corollary information on LIA glacier activity is available from the Canadian Rocky Mountains (Luckman, 2000) and Alaska (Wiles et al., 1999a, 199b), and is only briefly reviewed here.

The earliest evidence for the onset of LIA glaciation dates to the 11th_{and 13}th Centuries in the Coast Mountains. Evidence recovered in Garibaldi Provincial Park by

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Koch et al. (2007a) indicates that Warren Glacier overran a valley-bottom forest in 1050 AD, reaching its maximum down valley extension by the 12th_{Century. This finding} agrees with radiocarbon dates presented by Ryder and Thomson (1986) from Klinaklini Glacier to the north, where organics were buried by a glacial advance in the 11th_{or early} 12th_{Centuries. Davis et al. (2007) examined the remains of a forest found in lateral} moraines at Coleman Glacier on Mt. Baker in the Cascade Range that indicate they were buried by an advance in 1000-1210 AD (ca. 940 14_{C yr BP).}

Sundry locations within the Pacific Coast Ranges indicate moraine construction during the 13th _{Century. Geobotanical dating techniques provide minimum dates for the} till surfaces within Garibaldi Provincial Park (Koch et al., 2007a; Koch, 2009) and at Bridge Glacier, where a late-13th_{Century date was assigned with lichenometry to the} outermost terminal moraine (Allen and Smith, 2007). Early-LIA glacier activity may have culminated earlier in the central Coast Mountains where Desloges and Ryder (1990) and Larocque and Smith (2003) estimate moraines were emplaced by the early 1200's AD. Contemporary glacial activity has also been documented further in the northern Coast Mountains, where Lewis and Smith (2005) and Jackson et al. (2008) report early-mid 13th_{Century advances took place.}

Lichenometric dates point to a subsequent advance throughout southwestern B.C. that ended in the early to mid 14th_{Century (Larocque and Smith, 2003; Lewis and Smith,} 2004b; Allen and Smith, 2007; Koch et al., 2007a). Corresponding dates have also been suggested from geobotanical evidence located on the slopes of Mt. Rainier by Burbank (1981), following concurrent discoveries at Cowlitz Glacier (Crandall and Miller, 1964) and in the Dome Peak area (Miller, 1969).

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Several glaciated valleys in western B.C. contain evidence of a 15th_Century advance. Wood collected from the lateral margins of Lillooet Glacier supports moraine construction at this time (Reyes and Clague, 2004). Further to the north, organic layers buried beneath a fen down valley of Berendon and Frank Mackie glaciers correspond with a 15th_{Century advance (Clague and Mathews, 1992; Clague and Mathewes, 1996).}

In the Mt. Waddington area Larocque and Smith (2003) found evidence for advances from 1506 to 1524 AD and from 1562 to 1575 AD. Synchronous events were also recorded in the northern Cascade Mountains from moraines situated on Dome Peak (Miller, 1969), Mt. Baker (Heikinnen, 1984; Davis et al., 2007), and Mt. Rainier

(Sigafoos and Hendricks, 1972; Burbank, 1981). Following these advances, Larocque and Smith (2003) propose two moraine-building events, one from 1597-1621 AD, and a second from 1657 to1660 AD. Corresponding moraine-building events recorded within fen sediments in the northern Coast Mountains (Clague and Mathews, 1992; Clague and Mathewes, 1996) and from Mt. Baker (Easterbrook and Burke, 1971; Fuller, 1980) offer additional evidence for an early 17th_{Century glacier front oscillation.}

The majority of LIA moraines from the southern Coast Mountains date to the 18th Century. Glaciers advancing down valley at this time carved still visible trimlines

through subalpine forests. Allen and Smith (2007) and Koch et al. (2007a) report on an advance in the early decades of the 1700's AD, which slightly post-dates a corresponding advance reported in Tweedsmuir Provincial Park (Smith and Desloges, 2000). At sites in the northern Coast Mountain, there is evidence to suggest that this event culminated slightly later in 1760 AD (Jackson et al., 2008). Contemporaneous glacier advances are described by moraines the Gulf of Alaska (Wiles et al., 1999a) and in the Cascade

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Mountains (Burbank, 1981; Heikkinen, 1984).

Moraines deposited after the 18th_{Century record less extensive readvances and} are characteristically located up-valley from terminal LIA deposits. Larocque and Smith (2003) report on two episodes of moraine construction in central B.C. from 1821-1837 AD and 1871-1900 AD. Two moraines dating to the 1900's AD are reported from Bridge Glacier (Allen and Smith, 2007), and in the Mt. Waddington area moraine construction is also reported between 1915-1928 AD and 1942-1946 AD (Larocque and Smith, 2003). On Vancouver Island, Lewis and Smith (2004b) propose moraine emplacement in the 1930's AD.

Holocene Glacial Activity in PNA

Canadian Rocky Mountains

In the Canadian Rocky Mountains the earliest indication of glacier activity in the last millennium dates to the 12th_-13th_{Centuries. Luckman (1993, 1995, 1996) reports on} a sustained advance from 1142-1350 AD at Robson and Peyto glaciers. Depressed summer air temperatures in the 1690's AD, and an interval of increased precipitation from 1660-1690 AD, may have prompted early 1700's AD moraine construction (Luckman, 2000). During the 18th_{Century extensive advances are recorded at South} Cirque Glacier (Bednarski, 1979), Yoho Glacier (Bray and Struik, 1963), Angel Glacier (Luckman, 1977); as well as in Maligne Ice Field (Kearney, 1981), the Premier Range (Watson, 1986), at Mt. Robson (Heusser, 1956; Luckman, 1995), Peter Lougheed and Elk Lakes Provincial Park (Smith et al., 1995), at Dome Glacier, (Luckman, 1998), at

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Manitoba Glacier (Robinson, 1998) and at Stutfield Glacier (Osborn et al., 2001). Regionally, glaciers in the Canadian Rocky Mountains built their outermost moraines in the mid-1800's AD (Luckman, 2000). Dendroclimatic reconstructions suggest that this advance occurred in response to decreased summer air temperatures during preceding decades (Luckman, 2000). Several moraines record readvances in the latter half of the century, from 1840-1900 AD, at Mt. Robson (Luckman, 1995) during an interval of increased regional precipitation (Luckman, 2000).

Alaska

Evidence of LIA glacier activity in Alaska indicates that glaciers began to advance down valley between 1100 and 1200 AD in the Wrangell Mountains (Wiles et al., 2002) and in the Kenai Mountains (Wiles and Calkin, 1994). Indications of glacial activity during the 13th_{Century are found in the Gulf of Alaska (Wiles et al., 1999a),} western Prince William Sound (Wiles et al., 1999b), Wrangell Mountains (Wiles et al., 2002), Kenai Mountains (Wiles and Calkin, 1994), and Brooks Range (Evison et al., 1996). Mid-LIA extensions during the 15th_{Century are indicated earlier in the century by} Calkin et al. (2001), at a time when the Kenai Mountains were experiencing increased precipitation and decreased summer air temperatures (Wiles and Calkin, 1994). Denton and Karlén (1977) and Evison et al. (1996) present evidence for the down valley

movement of glaciers in Alaska in the 1400's AD. Subsequent advances were also noted during the 16th _{Century (Denton and Karlén, 1977; Evison et al., 1996). The Kenai and} the Wrangell Mountains experienced and increased ice-cover in the mid-1600's AD (Wiles and Calkin, 1994; Wiles et al., 1999a; Wiles et al., 2002) and the St. Elias

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Mountains (Reyes et al., 2006).

Summary

Ongoing glaciological research in the glaciated basins of coastal B.C. has revealed an increasingly complex story of glacier activity over the last 10,000 years (Menounos et al., in press). With persistent sampling effort and increased exposure of subfossilized wood, regionally synchronous events such as the “Tiedemann Advance” and the LIA are suggestive of sustained intervals of wet and cool climatic conditions in the late-Holocene (Walker and Pellat, 2003). Other glacial events, however, have no counterpart in climatic history. Notable in this regard are records of glacier expansion in the early-Holocene (Reasoner et al., 2001) and during the FMA (Reyes et al., 2006), when lake sediments record warmer temperatures than present. Dendroclimatic reconstructions from this region interpreted within the context of the present record of glaciation, suggest that regionally the LIA glacial interval coincides with the coldest decades of the past centuries and a notable period of moraine construction in both the Coast Mountains (Larocque and Smith, 2003) and the Canadian Rocky Mountains (Luckman, 2000).

The detailed history offered from Coast Mountain glaciological research for the LIA, perhaps, may serve as an analog to glacier activity during the entire Holocene. In agreement with the original proposal by Mathes (1939), it seems that the Holocene is best described as a time of numerous “little ice ages”. This research aims to test this

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Chapter 3: Late-Holocene glacial activity of Manatee Valley,

southern Coast Mountains, British Columbia

Introduction

Southwestern British Columbia (B.C.) has experienced significant volumetric losses in glacial ice over the last century (Schiefer et al., 2007; Vanlooy and Forster, 2008), creating a striking visual contrast between the extensive distribution of late-Holocene till and the presently retracted ice fronts (Mathews, 1951; Ryder and Thomson, 1986). Since the beginning of mass balance observations in the mid-1960's, the dynamics of several B.C. glaciers have been related to annual climate variations, mainly summer air temperatures and winter precipitation totals (Letréguilly, 1988). The brevity of these records, however, prevents a reliable characterization of alpine glacierization on longer time scales.

Over the past decade, dendroglaciological research from coastal B.C. mountains has contributed greatly to the discussion about the variability of alpine environmental conditions throughout the past 10,000 ka cal. years BP (Walker and Pellatt, 2003;

Menounos et al., in press). Several studies demonstrate the ability of dendroglaciology to extend glaciologic records of the Coast Mountain glaciers through the Holocene, by providing accurate age determinations for glacial deposits (Ryder and Thomson, 1986; Smith and Desloges, 2000; Larocque and Smith, 2003; Lewis and Smith, 2004; Allen and Smith, 2007; Koch et al., 2007a, 2007b; Jackson et al., 2008).

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investigations at four glacier forefields in the Manatee Valley area of the southern B.C. Coast Mountains. Reconnaissance investigations in 2006 led to the discovery of buried subfossil stumps and forest detritus within the glacier forefields. A second trip in 2007 provided an opportunity to search for additional wood samples and to detail the age of Little Ice Age (LIA) moraines in this region. In this chapter I present and compare the results of my research to other paleoenvironmental records from B.C. mountains.

Research Background

Dendroglaciology describes the application of tree-ring dating principles to assign ages to glacial sediments and landforms. Lawrence (1946) pioneered early efforts and used the total number of annual rings within first-colonizing trees as a minimum estimate of surface age. Within the Canadian Rocky Mountains, historical records and

accessibility encouraged the refinement of dendroglaciology to develop LIA glacial histories (Heusser, 1956; Smith et al., 1995; Luckman, 2000). By comparison,

dendroglaciological applications were employed only rarely until recently in the Coast Mountains (Mathews, 1951; Ryder and Thomson, 1986; Smith and Laroque, 1996). Within the last decade, however, extensive ice front retreat and focused attention on exposed dendroglaciological evidence has allowed for the development of detailed records of glacier behaviour throughout the Holocene (Larocque and Smith, 2003; Lewis and Smith, 2004; Reyes et al., 2006; Allen and Smith, 2007; Koch et al., 2007a, 2007b; Jackson et al., 2008).

The renewal of alpine glaciation around 6000 14_{C years BP following} early-Holocene warming, was defined by Porter and Denton (1967) as the “Neoglacial”.

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Although the Neoglacial was assumed to represent the initial expansion of glaciers in the Holocene (Ryder and Thomson, 1986), recent research has revealed ice fronts did

advance during the early-Holocene (prior to 6000 14_{C years BP) in the southern and} northern Coast Mountains (Laxton et al., 2003; Smith et al., 2005; Koch et al., 2007b), in the Canadian Rocky Mountains (Luckman, 1988), and in the North Cascade Range of Washington State (WA) (Béget, 1981; Heine, 1998; Thomas et al., 2000). Because environmental reconstructions argue for the dominance of warm and dry conditions during this interval (Clague and Mathews, 1989; Hebda, 1995; Walker and Pellat, 2003), Reasoner et al. (2001) and Menounos et al. (2004) suggest this advance was short-lived.

The onset of regional glacial conditions in the Holocene corresponds to the 6000-5300 14_{C yrs BP interval. Coined the “Garibaldi Phase” by Ryder and Thomson} (1986), the original interpretation of glacier expansion during this period was based upon radiocarbon evidence from sites located within Garibaldi Provincial Park (Stuiver et al., 1960; Lowdon and Blake, 1968, 1975). In their conservative interpretation, the term “phase” was preferred over “Advance” because the magnitude of the event was unknown. Recent discoveries from the northern (Smith, 2003; Smith et al., 2006) and southern Coast Mountains provide convincing evidence for a distinct interval of ice front expansion 6400-5100 14_{C yrs BP (Koch et al., 2007b). Paleobotanical reconstructions of} Holocene climate suggest a shift to wetter and cooler conditions occurred at 5000 14_{C yrs} BP (Spooner et al., 2002; Walker and Pellatt, 2003).

Based on reinterpretations of forests buried by glaciers in Garibaldi Provincial Park, recent data collected at Tiedemann Glacier, and the evaluation of sedimentation records of alpine lakes in southern B.C., Menounos et al. (2008) proposed a distinct

Late Holocene glacial history of Manatee Valley, Upper Lillooet Provincial Park, southern Coast Mountains, British Columbia

Upper Lillooet Provincial Park,

Southern Coast Mountains, British Columbia

Supervisory Committee

Abstract

Table of Contents

List of Figures

List of Tables

Acknowledgments

Chapter 1: Introduction

Chapter 2: Review of Dendroglaciologic and Lichenometric

Research in Pacific North America

Chapter 3: Late-Holocene glacial activity of Manatee Valley,

southern Coast Mountains, British Columbia